[Discuss] lvm snapshot cloning

[markw at mohawksoft.com]

>> From: discuss-bounces+blu=nedharvey.com at blu.org [mailto:discuss-
>> bounces+blu=nedharvey.com at blu.org] On Behalf Of

>> If you use a dedicated high speed SATA or SAS drive, you may get a
>> whopping 160MB/s. That's 1 hour 49 minutes.
>
> Take it for granted, you won't be stuck at USB2 speeds.  USB has
> universally
> (to the extent I care about) been replaced by USB3, since about 2-3 years
> ago.  The bottleneck is the speed of the external disk, which I typically
> measure at 1Gbit/sec per disk.  (You can sometimes parallelize using
> multiple disks depending on your circumstances.)  It's random IO that
> really
> hurts you.

If you can get more than 160MB/s (sustained) on anything other than exotic
hardware, I'd be surprised. 1Gbit/sec per disk sustained is currently not
possible with COTS hardware that is available.

Transfer rate is not "sustained," and "peak" is not "sustained." Yes, if
can can manage to read/write to disk cache, you can get cool performance,
but if you are doing backups, you will blow out cache quite quickly.